Question

我有已发布的应用程序我还没有添加 DATABASE_VERSION 。

现在我想用3个表中的一些新行（~100行）更新数据库

我在升级和删除新数据库文件时删除数据库。

我在资产中有数据库文件。但在升级应用程序时它停止工作。实际上dubug app工作正常，但发布apk停止工作。

这是我的代码

private static String DB_PATH = "/data/data/my.package.name/databases/";

private static String DB_NAME = "file.sqlite";
private static final int DATABASE_VERSION = 2;

private SQLiteDatabase myDataBase;

private final Context myContext;
 *
 * @param context
 */
public DataBaseHelper(Context context) {

    super(context, DB_NAME, null, DATABASE_VERSION);
    this.myContext = context;
}

/**
 * Creates a empty database on the system and rewrites it with your own database.
 */
public void createDataBase() {

    boolean dbExist = checkDataBase();

    if (dbExist) {
//do nothing - database already exist
    } else {

 //By calling this method and empty database will be created into the default system path
 //of your application so we are gonna be able to overwrite that database with our database.
        this.getReadableDatabase();

        try {

            copyDataBase();

        } catch (IOException e) {

            throw new Error("Error copying database");

        }
    }

}

/**
 * Check if the database already exist to avoid re-copying the file each time you open the application.
 *
 * @return true if it exists, false if it doesn't
 */
private boolean checkDataBase() {

    SQLiteDatabase checkDB = null;

    try {
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    } catch (SQLiteException e) {

 //database does't exist yet.

    }

    if (checkDB != null) {
        checkDB.close();
    }
    return checkDB != null;
}

/**
 * Copies your database from your local assets-folder to the just created empty database in the
 * system folder, from where it can be accessed and handled.
 * This is done by transfering bytestream.
 */
private void copyDataBase() throws IOException {

 //Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open(DB_NAME);

// Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;

//Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName);

//transfer bytes from the inputfile to the outputfile
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }

//Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close();

}

@Override
public synchronized void close() {

    if (myDataBase != null)
        myDataBase.close();

    super.close();

}

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    myContext.deleteDatabase(DB_NAME);
    Toast.makeText(myContext,"done",Toast.LENGTH_SHORT).show();
    createDataBase();
}

Answer 1

我相信这是你的问题：

public void createDataBase() {
    ...
    this.getReadableDatabase();
    try {
        copyDataBase();
    } catch (IOException e) {
        throw new Error("Error copying database");
    }
}

this.getReadableDatabase()打开您的数据库以供阅读。然后，copyDataBase()尝试编写您的asset文件。但是，由于文件已打开以供读取，因此无法编写并出现错误。

因此，我认为您必须按如下方式更新createDataBase()：

public void createDataBase() {
    boolean dbExist = checkDataBase();
    if (dbExist) {
        //do nothing - database already exist
    } else {
        SQLiteDatabase checkDB = getReadableDatabase();
        checkDB.close();
        try {
            copyDataBase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}

Answer 2

如果您不关心旧数据库中的数据，则无需进行任何形式的升级或版本控制。只需更改文件名即可。因此，新的APK会创建一个新文件，您可以随时删除旧文件。

请注意，SQLiteAssetHelper可以帮助您复制内容。

在onUpgrade Sqlite Android上重新创建数据库

2 个答案: